1. Technical Field
The present invention relates to an apparatus for mounting solder balls on a plurality of connection pads.
2. Description of the Related Art
According to the related art, in order to form a solder bump on a connection pad for flip chip connection of a substrate such as a wafer, a circuit substrate, or the like, a solder paste has been screen printed and then has been subjected to a reflow process.
FIGS. 1A and 1B show a method for mounting solder balls according to the related art. According to the related art, a method in which flux is first allowed to be passed through a metal mask opening using a metal mask and a urethane squeegee to thereby be printed (See FIG. 1A), solder balls are mounted in a scheme in which they are positioned on the metal mask, are moved using a squeegee such as a metal wire, or the like, and dropped through the metal mask opening to thereby be seated on a pad having the flux applied thereto (See FIG. 1B), and bumps are then formed through a reflow process has been used.
However, in this method, an operation of separately recovering the solder balls after they are mounted on the mask is repeatedly performed, thereby causing reduction in a mounting speed of the solder balls.
Meanwhile, in accordance with the recent densification of semiconductor devices, a bump pitch having a micro-pitch of about 200 micron or 150 micron has also been required. When a solder paste is screen printed at the micro-pitch, a bridge between the bumps or an attachment of the solder paste to a printing mask occurs. Therefore, it has become difficult to form the solder bump at the micro-pitch by screen printing.
In order to solve this problem, methods of directly mounting solder balls on connection pads have been suggested as a method for forming the bump having the micro-pitch.
As one of the suggested methods, there may be a method of sucking and carrying solder balls using a suction jig and mounting the solder balls on connection pads, which is a method performed on connection pads for board mounting on an external connection terminal side of a ball grid array (BGA). Adhesive flux for soldering is previously applied to the connection pad, and the solder balls are attached and fixed to the connection pads by the adhesive flux. Then, the solder balls reflow to thereby form the bumps.
However, in this case, the solder ball has a large diameter of about 0.3 to 0.7 mm. It is necessary to allow solder balls for a micro-pitch to have a diameter of 100 micron or less. When the diameter of the solder balls becomes small as described above, aggregation occurs between the solder balls due to the action of static electricity or the solder balls may not be accurately sucked in a suction port of the suction jig due to the flow of air. Therefore, the suction port of the suction jig should also have a minute size, which causes an increase in a processing cost.
As another method suggested owing to this reason, there may be a method of mounting solder balls in openings of a mask disposed on a substrate using a head apparatus, which is a separate solder ball storing apparatus. That is, flux is first applied to a connection pad of the substrate and the connection pad and a metal mask are then arranged to and overlapped with each other. In this state, the solder balls drop from the head apparatus disposed over the metal mask onto the openings of the metal mask. An appropriate number of solder balls drop from the head apparatus, which is a separate container having an opening such as a slit, or the like, formed at the bottom thereof, on the mask. One solder ball drops onto each of the openings of the mask and is disposed on the connection pad arranged to the opening, such that it is attached and fixed to the connection pad by adhesive flux applied thereto.
In the method using the solder ball supplying head apparatus, the mask and a solder ball supplying head should necessarily have an interval of about a solder ball diameter or less maintained therebetween without being in contact with each other. However, in a method of maintaining an interval between the mask and the head as described, the solder ball is inserted therebetween, which causes deformation. Particularly, in the case of a circuit substrate such as a resin substrate, or the like, a bent degree thereof is large, and non-uniformity in thickness thereof is relatively large. Therefore, when a target substrate has a large size, it is very difficult to uniformly secure an interval between the mask and the head over the entire substrate, such that it is substantially impossible to avoid a problem that the solder ball is inserted between the mask and the head.
The manufacturing and the operation controlling of a separate head apparatus corresponding to the solder ball storing container may also impose a burden on users.